The field of fire protection presents several problems to the designer of major valves utilized in such systems. The high fluid volume required to overcome fires dictate large pipe and valve diameters, which in turn translates to a need to control large operating pressures. To reduce the forces required to transition a valve from a closed to open state (and in certain cases from open to closed state) hydraulic valves have been developed. In a hydraulic valve, pressure is applied to a control chamber, and is applied to a sealing member. Release of the pressure causes the sealing member to open, and allow distribution of the primary firefighting fluid into the firefighting system. A base valve may be utilized for different functions and/or systems, such as deluge, wet system, dry/pre-action valves, pressure reducing, deluge reducing and deluge on/off applications. The base valve is configured to fulfill those varied functions by external connections and components, collectively known as ‘trim’.
The base valve has at least a valve body, an inlet in fluid communication with an inlet chamber which can hold a fluid supply, and an outlet chamber which can receive fluid from the inlet chamber and controllably pass the fluid to an outlet. The fluid in the input will be referred to herein as a ‘primary’ fluid. A valve may be in a “closed”, (equivalently known as “standby”) state where the valve impedes flow of fluid between the inlet and outlet, and an “opened”, (equivalently known as “activated”) state in which fluid communication is established between the input and output chambers, and fluid is allowed to flow between the input and the output.
For various reasons that will be explained below, If a firefighting system base valve is activated due to fire, there is a risk that the valve will be closed, unless a latch mechanism is provided to maintain the valve in an open state as long as it is needed, and allow a relatively simple and efficient reset operation. Various embodiments of the present invention are directed to providing a latch for that purpose, and more particularly to a latch involving fluid and fluid pressure manipulation to achieve the desired result Such a latch will be referred to hereinunder as a hydraulic latch, manual reset device, (equivalently referred to as a latch, for brevity).
Nowadays diaphragm valves are in common use and for brevity and simplicity of understanding of the principles of the present invention, such valves will be utilized by way of example in these specifications; however the skilled in the art will readily recognize that the principles disclosed herein are applicable to any hydraulic valve having a control chamber.
FIG. 1 depicts an isometric view of a common diaphragm valve 10, an hydraulic latch 12, and an activating device 14. Notably, while the hydraulic latch 12 shown in the drawing may be any type of hydraulic latch, the drawing depicts one embodiment of the present invention.
The valve 10 in the example acts as the base valve of a fire fighting system, and comprises an inlet chamber 102 and an outlet chamber 104, separated by diaphragm 100. The diaphragm has a bottom surface 106 and a top surface 108, the top surface forms a part of a diaphragm chamber 110. The top surface of the diaphragm is exposed to the pressure in the diaphragm chamber 110, which acts as a control chamber. During the system standby state the valve impedes water flow. The top surface 108 of the diaphragm is exposed to the pressure of the fluid in the control chamber. If the pressure in the inlet chamber is equal to the pressure in the diaphragm chamber the valve is in standby (equivalently referred to as closed) state. The valve is closed because a larger area of the diaphragm top surface 106 is exposed to fluid pressure than the area exposed to the fluid pressure at the bottom surface of the diaphragm 108 (any force from the outlet chamber is considered negligible in this example). Thus the diaphragm exerts pressure on a bridge section 103 which separates the inlet chamber and the outlet chamber, and forms a seal therebetween. If the pressure in the diaphragm chamber is reduced to the point that the force exerted by it on the diaphragm is lower than the pressure exerted on the diaphragm by the fluid in the inlet chamber, the diaphragm will be pushed away from the bridge, allowing fluid to flow between the inlet and outlet chambers, and the valve is thus in the ‘open’ state. It is seen therefore that the pressure in the diaphragm chamber controls the operation of the valve, and thus the diaphragm chamber acts as a control chamber to control the valve state. Other mechanisms of control chamber operated valves abound, and the invention extends thereto.
It is common to couple fluid from the primary fluid supply to the control chamber 110. However the pressure supplied to the control chamber may come from any desired source, and does not have to come from the fluid supply side of the firefighting system. However the arrangement of supplying the fluid from the system supply side is one of the most common embodiments today, therefore these specifications shall use such an arrangement by way of example.
It is common to supply the primary fluid to the control chamber via a fluid path that offers a certain flow restriction 112, and to activate the valve by allowing the fluid to drain out of the control chamber via a less restrictive fluid path 114. The more restricted path 112 providing pressure to the valve control chamber will be referred to as the control supply path, and the lower restriction path 114 which is utilized to relieve the pressure from the valve control chamber by the activating device 14 will be referred to as the activating path.
The pressure in the control chamber (such as in the diaphragm chamber of a diaphragm valve) is controlled by an activation device 14 which controls flow in the activating path. Under normal conditions, when the valve is in standby mode, the activating device is closed, and the pressure in the base valve 10 control chamber is kept at sufficient level to maintain the valve in closed state. When a fire is detected, the activation device opens, providing pressure relief to the fluid in the control chamber via the activating path, which in turn allows the valve 10 to change to an open state. As the activation path offers lower flow resistance than the control supply path, the pressure in the control chamber will be sufficiently low to keep the base valve open, as long as the activation device 14 is open. However if the activating path 114 becomes more restrictive that the control supply path 112, the fluid from the control supply path will pressurize the control chamber and force the base valve 10 to close. Common embodiments of the activating devices include a solenoid, a dry pilot actuator, and the like.
Dry pilot devices rely on lose of pressure in the distribution system connected downstream from the base valve, to activate the valve. In certain systems a low pressure fluid is contained in the distribution system and when this pressure is released a fire is assumed, and a dry pilot devices which senses the pressure drop activates the base valve. Dry pilot valves are considered reliable without the need for electrical current, however they are susceptible to closing due to pressure buildup in the distribution system by the incoming primary fluid. An example of a dry pilot valve, and a limited function latch, is disclosed in U.S. Patent Publication 2014/0182865 to the present inventor, which is incorporated herein by reference.
Many activation devices 14 depend directly or indirectly on electrical power. Voluntary or involuntary loss of electrical power is extremely common in case of fire. There is therefore a high risk that the activation device will stop operating due to loss of electric power, or due to re-pressurization in the case of a dry pilot valve. Such stoppage will close the activation path pressurizing of the diaphragm chamber, and as pressure builds up in the control chamber from the control supply path, the valve will again transition to a closed state, cutting fluid flow to the system when it is most needed.
To mitigate this risk, the activation device may be coupled to the valve via the latch. The latch 12 acts to control pressure transfer from the system input to the control chamber. As a general rule, after the base valve 10 is activated, i.e. transitions to an open state, the latch acts to block pressure rebuilding in the control chamber 110, and requires a manual operation in order to reset the state of the base valve, regardless of the state of the activation device 14.
Several latch mechanisms are known in the art. By way of example Bermad Water Control Solutions (Kibutz Evron, Israel), and Inbal Valves of Rishon LeZion Israel make latch devices. Those devices rely on blocking fluid supply to the control chamber after the valve is activated. Solution based solely on closing the water supply to the control chamber has several drawbacks, most significant of which is the risk of even a small leak in the latch may re-close the base valve 10 after the activation device has been closed. Additionally, a system fluid shock wave (known in common parlance as ‘water hammer’), which will cause the force exerted on the diagram bottom by the pressure wave to exceed the force exerted from the control chamber, causing false tripping.
Thus there is a clear, yet heretofore unresolved need, for a positive resetting activated hydraulic latch that will ensure that after activation of a valve in a fire fighting system only manual operation will allow closure of the valve.